We modify the behaviour of the virtual ant introduced by Langton  by forcing it with periodical binary sequences. The turning direction of the ant at the ith iteration depends on whether the "ith" element of the binary sequence is zero or one. An overwhelming variety of frieze-like trajectories is obtained. Thus, this system is a novel prototype of high complexity resulting from simple rules. If the forcing is described by a real-valued parameter p, then any computationally feasible change "delta p" renders completely different patterns. Thus, sensitivity with respect to the control parameter can be conjectured to be infinitely large.